A technique, in which two display panels overlap each other and an image is displayed on each display panel based on an input video signal, is conventionally proposed to improve contrast of a liquid crystal display device (for example, see Unexamined Japanese Patent Publication No. 2008-191269). Specifically, for example, a color image is displayed on a front-side (observer-side) display panel in two display panels disposed back and forth, and a black-and-white image is displayed on a rear-side (backlight-side) display panel, thereby improving contrast. In the liquid crystal display device, smoothing processing of spreading locally a portion having a high signal level of the input video signal by several pixels is performed on the video signal supplied to the rear-side display panel in order to reduce a display defect caused by parallax.